Type locality and use of name: The name Patoka Formation was first used in a stratigraphic column by Wier and Gray (1961). The type locality (Wier, 1961, 1965) includes numerous exposures of parts of the formation along the tributaries of the Patoka River near Patoka in Gibson County. Other good exposures are along the tributaries of White River near Hazelton.
Rocks now recognized as belonging to the Patoka Formation were called the Merom Group in southern Indiana by Logan (1932) and were included in part of the Shelburn Group of Cumings (1922).
Description: The Patoka Formation is a southward-thickening unit of shale, sandstone, clay, limestone, and coal. The formation consists of all rocks above the West Franklin Limestone Member of the Shelburn Formation and below the Carthage Limestone Member of the Bond Formation. It comprises in ascending order the Ditney Coal, Vigo Limestone, Dicksburg Hills Sandstone, Raben Branch Coal, and Parker Coal Members and includes unnamed beds of shale, clay, and sandstone. Shale and sandstone make up more than 85 percent of the formation. The formation ranges in thickness from 100 feet (30 m) in northern Sullivan County to 310 feet (94 m) in southwestern Posey County.
Correlation: The Patoka is correlative with the upper part of the Modesto Formation of Illinois and the middle part of the Sturgis Formation of Kentucky.